1309 results found for Ideas For Design, displaying items 1 - 20
June 25, 2009 Triple-Current-Modulation Delta VBE Thermometry Cancels Ohmic Error Sources
Delta VBE-based ( VBE) thermometry1,2,3,4 is based on this classic bipolar junction I/V/T relationship: For an ideal transistor, the VBE corresponding to ratiometric change in collector current (I2 / I1) is exactly proportional to absolute temperature: VBE = 198.4 µV * °K * LOG10(I2 / I1). Because cheap, common, and robust small-signal transistors conform closely to the ideal model, circuits that exploit the “PTAT (Proportional...
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W. Stephen Woodward
June 25, 2009 Logic-Level Signals Shifted To Dim ?48-V LED Driver
The main source of power in a telecommunications system is -48 V. This source’s negative polarity and its large magnitude with respect to ground pose a challenge when designers want to use low-power ICs in the telecom system’s application circuits. Fortunately, the emergence of high-voltage ICs—with operating voltages of 75 V and higher—has enabled the use of simple biasing techniques in designing circuits for -48-V systems. The technique described here provides...
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Ahmad Ayar
June 25, 2009 Seamless Power Switcher And Battery Charger Solution Targets Portable Devices
In today’s world, there are many applications for portable devices. These devices must have extremely low or no battery drain when turned off and need to charge their on-board batteries when connected to an external power supply, whether the device is turned on or not. This circuit provides seamless switching from batteries to external power and provides a simple charging solution. In addition, there are several output signals for a microcontroller (MCU). This...
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Jim Wilson
June 11, 2009 Spice Model For An Ideal Transformer Allows Bi-directional Operation
This Idea For Design provides an alternative to an earlier IFD that noted that Spice does not have a device model for an ideal transformer (“A Spice Model For The Ideal Transformer”). The author explained, “Instead, Spice provides a coupled-inductor model in the K statement that includes self and mutual inductances.” The author’s proposed solution is a model that...
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Ken Hatch
June 11, 2009 Redundant Power-Supply Diode Features Fanless Passive Cooling
A Schottky diode is an excellent way to connect multiple batteries or dc power supplies to a load. With a forward-biased “or” diode between each supply and the load, faults are isolated. Weak, low, or shorted supplies can’t sink current from the other supplies. Unfortunately, the heat produced by a diode can be difficult to remove in some applications. This circuit was created to reduce the heat dissipated by a power-supply “or” diode in a redundant 50-V...
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Daniel Gomez-Ibanez
June 11, 2009 Charge-Pump VCO Increases Parts Count But Saves On Cost
This charge-pump voltagecontrolled oscillator (VCO) has a number of neat features: single positive power-supply operation, positive VCO reference voltage, fast response, high linearity, temperature compensation, and open collector output. Seldom are all of these features present simultaneously. Though the component count is relatively high compared to commercially available devices, cost is low because all components are garden variety. Central...
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Jim Keith
May 21, 2009 Current-Mode Multiplier/Divider Design Eschews Passive Components
This circuit design for a current-mode analog multiplier/ divider is based on current-controlled conveyors (CCCII) and a second-generation current conveyor (CCII). No passive components are used. Analog multipliers and dividers are important building blocks in signal processing and are widely used in modulation systems. Also, for the same two inputs, the multiplier changes to a squaring circuit, which provides the energy content of the signal. ...
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Abhirup Lahiri
May 7, 2009 Monitor Transformer Winding's Temperature Without A Sensor
The use of a copper winding as a temperature sensor is not new. The traditional technique is to disconnect the ac power and the load and to quickly make the measurement using an ohmmeter. But the circuit presented here goes further. It can make the measurement in-circuit and in real time. The resistance value is derived by injecting a small dc current into the monitored winding and measuring the resulting dc potential. However, care must be taken to avoid...
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Louis Vlemincq
May 7, 2009 Simple Technique Drives Multiple LEDs From One Processor Pin
Driving multiple LEDs with one microprocessor GPIO pin is a well-known technique. Typically, designs perform this task by issuing pulse widths and clocks of differing durations and employing multiple RC networks to distinguish between them. The design described here is much simpler. The microprocessor pin is connected to the clock of a multipleoutput sequential counter (see the figure). In its...
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Christopher Paul
May 7, 2009 Step Down A Negative Voltage Without Using An Inductor
When you need to step down a negative voltage in a lowcurrent application, a non-inductor configuration offers two advantages: ease of use and a low number of external components. Such step-down converters can be implemented with two chargepump devices. The first produces a positive output by doubling and inverting the negative input voltage, and the second acts as an inverter to produce the desired negative output (...
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Budge Ing
, et al.
April 23, 2009 Capacitor-Powered Electronics Is At The Core Of Green Design
The concept of using supercapacitors (also known as ultracapacitors, supercaps, etc.), and replacing the batteries in portable micropower applications,1 is gaining momentum. In fact, it has become one of the more noticeable technical trends of recent time. Supercapacitors, such as the BOOSTCAP ultracapacitors from Maxwell Technologies or DYNACAP from ...
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Alexander Bell
April 23, 2009 New Math Technique Increases Temperature Accuracy Over 20,000%
Thermistors are extremely nonlinear devices. Because of the limitations of the mathematical model used, the devices’ ultimate accuracy is hardly ever fully realized due to the extra computational burden required to calculate the temperature from an accurate resistance reading. Fortunately, a minor modification to any thermistor equation will provide a worthwhile improvement in overall accuracy. This article shows how an improved mathematical model...
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Elio Mazzocca
April 23, 2009 Sensor Signal Converter Outputs Both NPN And PNP Signals
Matching a sensor interface with a programmable logic converter or controller hardware that can accept only one type of input—npn or pnp—can be difficult. The last-stage modification circuit described here solves this problem. Designers can use it to convert an npn input to a pnp type or incorporate it in the last stage of the sensor design to generate both npn and pnp outputs. The npn and pnp transistors used in the circuit should be highcurrent- gain (hfe >...
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Shyam Sunder Tiwari
April 9, 2009 Switching Circuit Increases Number Of USARTs Available From MCU
This design builds on a previously published Idea for Design (“Talk To Multiple Devices With One UART”). Our solution allows you to increase the number of USARTs (universal synchronous, asynchronous receiver/transmitters) available on a microcontroller with minimum hardware. Typical 8- and 16-bit microcontrollers have one programmable USART for communication. But designers...
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Ashish Aggarwal
, et al.
April 9, 2009 Simple Solution Provides PWM Signal Fault Protection
This idea was created to solve a design problem we faced a few months ago. The circuit we were working on was used to steer an H-bridge that was controlled by a TMS320F2810 digital signal processor (DSP). During the final phase of the design, we discovered by chance that everything worked fine when the circuit was initially powered. However, if it was powered off for 5 to 15 seconds and then powered on again, the circuit started draining a lot of current...
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Arturo Mediano
, et al.
April 9, 2009 Simulated Grounded Inductor Needs No External Capacitors
Inductors designed with active elements are very desirable to designers today because conventional spiral inductors are too big, too heavy, and too costly, and they require tuning. During the last few decades, various grounded inductors have been created using different high-performance active building blocks, such as operational amplifiers and operational transconductance amplifiers. But op amps suffer from a finite gain-bandwidth product (GBP) and GBP interdependence,...
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Abhirup Lahiri
March 26, 2009 Precise Current-Transmitter/Source-Sink Calibrator Has Wide Compliance Range
Many industrial and control applications use analog current loops as the physical link for measurements and actuator control. Although several ranges are used, the most popular is still the 4- to 20-mA standard. Loop accuracy depends on the transmitter’s ability to transform the sensor signal to a current. It also depends on the stability of the current-transfer function (measured at the receiver) with respect to temperature, physical length of...
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Alfredo Saab
, et al.
March 26, 2009 Oscillator Delivers Four Multi-Phased, Equal-Amplitude Sine Waves
One application I recently dealt with needed multiple phases of sine waves, all of equal amplitude. I considered 45°, 60°, and 90° differences, but decided 60° was the best solution. I scoured the Internet for a circuit. Unfortunately, while multiple phases exist, and the topologies are legion, no topology offered sine waves of equal amplitude with a 60° phase shift. I thought the solution would look like a common three-op-amp phase-shift oscillator, so that was...
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John Guy
March 26, 2009 Alarm Sounds When Refrigerator Door Remains Open Too Long
Not properly closing a refrigerator door will no doubt invite huge electricity bills. This gadget is an alert device that beeps if you leave the refrigerator door open for more than 20 seconds. When the door opens, the lamp illuminates and the IC (a 4060B counter/oscillator) starts counting down. After a preset delay of 20 seconds, the piezoelectric buzzer beeps intermittently for 20 seconds and then stops for the same amount of time. This cycle...
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T.A. Babu
March 12, 2009 "Unstable" Power Supply Simulates Solar Panel Behavior
This power supply may seem a bit strange, since it’s not stable in voltage or in current. However, it simulates the behavior of a solar panel and can be very useful if you’re working with a solar-powered device on a rainy day. A solar-panel circuit can be represented by a current generator and some diodes (Fig. 1a). The short-circuit current depends on the cell type and illumination. The open circuit...
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Giovanni Romeo
, et al.
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